1. Find the molar mass of SO₂:
* Sulfur (S) has a molar mass of 32.06 g/mol.
* Oxygen (O) has a molar mass of 16.00 g/mol.
* SO₂ has a molar mass of 32.06 + (2 * 16.00) = 64.06 g/mol
2. Calculate the number of moles of SO₂:
* Moles = mass / molar mass
* Moles = 72 g / 64.06 g/mol
* Moles ≈ 1.124 mol
3. Convert moles to molecules using Avogadro's number:
* Avogadro's number is 6.022 x 10²³ molecules/mol
* Number of molecules = moles * Avogadro's number
* Number of molecules ≈ 1.124 mol * 6.022 x 10²³ molecules/mol
* Number of molecules ≈ 6.77 x 10²³ molecules
Therefore, approximately 6.77 x 10²³ molecules of sulfur dioxide are present in 72 g of the substance.
